Alignment of surfaces is a perennial problem in a variety of fields, ranging from construction to interior decorating. Alignment is necessary for walls that should be perpendicular to a floor, or otherwise plumb. Masonry and brick-laying practitioners are well aware of the importance of plumbed and aligned surfaces and chalk lines. A home interior decorated with pictures and other wall ornamentation has a much better appearance when the ornamentation is aligned, especially with respect to vertical or horizontal alignment. Many mechanical and electrical alignment devices are available, including laser devices. Some of these products are cumbersome, others are not as useful as they could be. Chalk lines, for example, are undesirable for use in finished, interior areas.
Several aspects of alignment-product performance, and in particular of laser-alignment products, that could be improved are the width, brightness and straightness of the laser light. A visible, straight laser line may be limited in its brightness over a distance, and may also tend to defocus and become dimmer as a user works away from the source of the laser. Rotating lasers are used to project lines on walls perpendicular to the direction of propagation of the laser. Thus, such devices may have limited utility or may not work in confined spaces requiring a longer alignment tool.
Moreover, a conventional laser is not well-equipped for projecting a flat or planar beam of light. The essence of laser light is that it is coherent or substantially monochromatic, that is, of a single wavelength or a narrow wavelength band. Thus, when a beam of laser light is refracted through a prism, the prism output is not a spreading of the beam as with ordinary “white” light, but rather a coherent, focused beam, very similar to the input. The laser beam is thin and is only usefully visible when projected onto a surface.
Another aspect that could be improved is the inability of laser devices to work around obstructions. That is, if a wall-hanging, such as a picture frame, interrupts the laser beam, it may be blocked from further projection. Therefore, it is necessary to mark locations or heights, one by one, rather than working with the actual objects, in order to align them. Obstructions may include moldings placed in a doorway, picture frames in the way of those being aligned on one horizontal line, the operator of the device, other obstacles, or even textured or stuccoed surfaces on interior walls.
There are devices that direct a laser beam parallel to but away from a surface requiring alignment. A marker device or detector component is then used to sight the beam and mark corresponding locations on the wall adjacent the beam. Use of such a device requires multiple components and at least two people, one to align the laser and another to mark the wall.
Some laser devices attempt to use a laser light in combination with a reference surface, in order to place the laser light in the same plane with the reference surface. Thus, U.S. Pat. No. 5,604,987 incorporates a laser light in a carpenter's level, so that the laser light projects in the same plane as a surface of the level. However, this requires the level to have an interrupted surface, rather than a flat surface. An interrupted surface that is not flat cannot be used as a reference plane.
A conventional laser beam alignment tool is not able to project its laser light in the same plane as a surface of the alignment tool. It would be desirable to use a straight laser line or a planar beam of laser light in the same plane as a surface of the laser alignment tool.